1. Field of the Invention
This invention relates to a shift lever assembly for changing the speed of a power take-off shaft of a tractor.
2. Description of the Prior Art
It is known in tractor design to use a power take-off shaft, hereinafter referred to as PTO, which is capable of being driven selectively at either of two standard speeds, namely 540 rpm and 1000 rpm. The drive for the PTO shaft is shiftable for the different speeds by a lever arrangement which the driver moves manually from his seat in the tractor cab.
In one such arrangement, two manual levers are provided which, when moved, for example, from the 540 rpm to the 1000 rpm position, must be handled three times, i.e. one lever is moved, then the other, and finally the first lever is again shifted. The system is complicated because it is necessary to design into any shifting arrangement a safety feature which prevents inadvertent movement from one speed to the other. This feature is needed because machinery which is to be driven by the PTO is adapted to operate at only one of the two standard speeds.